- IVI studies aim to find evidence about rotavirus disease burden, 
  vaccine safety, efficacy and cost effectiveness for policy makers

An infant is vaccinated against rotavirus in Vietnam.

Rotavirus is a leading cause of severe diarrhea among infants and children under five years of age. Globally, rotavirus disease claims the lives of an estimated 527,000 children each year, with most victims being children in developing countries who have limited access to health care.

The good news is that safe and effective vaccines against rotavirus have recently become licensed internationally, with several additional vaccines now under development. In order for these vaccines to reach those in need, however, it is important to understand rotavirus disease incidence and patterns, experts say.

According to World Health Organization (WHO) recommendations, local information is required to convince national public health policy makers to include the vaccine in their infant immunization programs.

In order to address this issue, the IVI is assisting with evaluations of vaccine safety, efficacy and cost effectiveness in Asian developing countries. The IVI’s Rotavirus Vaccine Program has also been gathering new evidence about rotavirus disease burden, including information on patterns of disease, cost of illness and distribution of different rotavirus strains circulating in local populations in Asian countries.

IVI scientist Shin Sunheang (second from left) works with 
local collaborators to evaluate the efficacy of a rotavirus vaccine
in children at a health center in Vietnam.

Specifically, the program aims to inform policy decisions on rational introduction of new rotavirus vaccines at country levels by studying disease burden, distribution of rotavirus strains, costs of illness, and the safety, as well as immune response, efficacy and cost-effectiveness of rotavirus vaccination. It also seeks to expedite the use of new generation rotavirus vaccines by accelerating the evaluation of new vaccine candidates in developing countries.

Currently, there are two licensed vaccines available: GlaxoSmithKline’s RotaRix®, and Merck’s RotaTeqTM. These vaccines are formulated for oral administration to infants. "Studies have shown that the two vaccines are safe and effective," said Dr. Paul Kilgore, a senior epidemiologist at the IVI. “If these new vaccines are integrated into infant immunization programs in Asia and Africa, they may prevent a major fraction of diarrhea-associated deaths and more than 80 percent of rotavirus-associated hospitalizations.”

Assessing rotavirus disease and vaccines in Vietnam
Two trials to measure the impact of rotavirus vaccines have been undertaken in Vietnam. 

The IVI has collaborated on a phase II trial of the GSK vaccine in children to determine the safety of and immune response to the vaccine in Vietnam. The IVI is also collaborating in a phase III trial of the Merck vaccine in 900 children in Nha Trang. The latter is part of a multi-country, double-blinded placebo controlled trial to assess the safety and efficacy of RotaTeqTM against severe rotavirus disease. The results of the trial, sponsored by PATH, will likely become available in mid-2009 when WHO and the international community make a formal recommendation regarding global scale use of the vaccine.

In addition to the RotaTeqTM trial in Vietnam, the IVI has initiated a population-based disease burden study through an enhanced rotavirus surveillance program in Vietnam. The study is designed to gather comprehensive data on the incidence and cost of illness due to rotavirus.

Based on the data from these trials and studies in Vietnam, the economic impact of a vaccination program will be assessed at the country level. Results of these studies will be provided to inform policy makers on decisions regarding the introduction of rotavirus vaccines in the country.

 “These studies will present important evidence in making decisions on a vaccination program to Vietnamese policy makers,” Dr. Kilgore said.

Estimating rotavirus incidence in Asian countries
The IVI also assessed the importance of rotavirus as a cause of hospitalizations among children through sentinel hospital-based surveillance studies in four countries (Cambodia, Laos, Mongolia and Sri Lanka). From March 2005 through February 2007, this study revealed that 25-56 percent of children under five hospitalized with diarrhea were infected with rotavirus. This study will be the foundation for estimating national rotavirus diarrhea incidence in these countries.

Earlier, the IVI conducted rotavirus surveillance in Korea to determine the prevalence of rotavirus disease. Two years of population-based surveillance, conducted in collaboration with Chonbuk National University during July 2002 to June 2004 in Jeongeup District, North Jeolla Province, found a high rotavirus rate of 46 per 1,000 hospitalized children under 5 years.

Another study of Korea’s National Health Insurance Corporation (KNHIC)’s national databases from January 1995 to April 2005 found children under five are hospitalized for diarrhea at a rate of 12/1,000, with infants six months or younger having the highest rates (38/1,000). ”With a large winter seasonal epidemic peak, these data suggest that a high proportion of childhood diarrhea in Korea is caused by viruses including rotavirus,” Dr. Kilgore said.

IVI scientists collaborated in a two-year hospital based study from August 2001 through July 2003 with the Chinese National Institute of Virology. This study found that rotavirus accounted for 49 percent of watery diarrhea cases in children under 5 years in five representative hospitals. Ninety-five percent of hospitalized cases occurred in children under 2 years.